1. Field of the Invention
The present invention relates to a method and apparatus for cleaning a substrate, such as a semiconductor substrate.
2. Background Art
When an interconnection pattern is formed on a semiconductor substrate during the course of manufacture of a semiconductor device, a resist pattern is formed on a metal film; e.g., Al or Cu. The semiconductor substrate is subjected to plasma etching via the resist pattern, thus forming an interconnection pattern.
In association with an increase in the packing density of a device, a sidewall protection film for protecting sidewalls of a pattern during plasma etching is formed thickly, thus improving a geometry into which the metal film is to be etched. In this case, an altered resist layer resulting from plasma etching of a pattern, such as an Al or Cu interconnection, tends to become more difficult to remove during a removal process subsequent to the plasma etching process.
FIG. 7 is a conceptual drawing of a cross section of a pattern for describing the tendency. A resist layer 73 adhering to the side surfaces of an aluminum interconnection pattern 72 on a substrate 71 acts as a sidewall protection film. Concurrently, an altered resist layer 75 adheres also to the sidewalls of a resist pattern 74.
In order to eliminate the resist after etching, the altered resist layer 75 has hitherto been removed by means of a wet etching method. However, there still remain residues of the altered layer that cannot be removed by the solubility of the resist in a chemical.
Alternatively, a single wafer processing cleaner has hitherto been employed. FIG. 8 is a conceptual drawing of an example of such a processing cleaner. In the cleaner, a substrate 82 to be cleaned is placed on top of a rotary stage 81, and chemicals are dropped from a chemical drop nozzle 83 onto the substrate 82. In the case of such a rotary method, structural limitations are imposed on introduction of ultrasonic cleaner for improving the removal.
The present invention has been conceived to solve the drawbacks of the related-art cleaning technology as described above. To this end, there is adopted a dipping method of introducing a chemical into a processing bath. A substrate to be cleaned is immersed in the chemical and exposed to ultrasonic waves, thereby improving a cleaning effect and promoting removal of an altered resist layer adhering to the substrate.